شرح ساينس الصف السادس الابتدائي لغات - الفصل الدراسي الثاني
شرح ساينس سادسة ابتدائي - ترم ثاني

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In This Lesson:
Water cycle
It is the continuous movement of water among different water reservoirs.
Water reservoirs
They are storage locations of water on Earth.

Water reservoirs include:
- Oceans. - Seas. - Lakes.
- Rivers. - Glaciers. - Soil.
- Rocks. - Living organisms. - Atmosphere.
▌The main processes and steps that move water among these reservoirs are evaporation, condensation, precipitation, runoff and collection.
▌All these processes and steps depend on energy and force.

The factors that affect the movement of water in the water cycle :
Solar energy :
▌The Sun is the most important source of energy that affects the water cycle.
▌The sunlight (solar radiation) that comes from the Sun includes thermal energy that causes the change of the state of water through the water cycle, where :
- During melting, when water changes from solid state (ice) to liquid state (liquid water), it gains energy.
- During evaporation, when water changes from liquid state (liquid water) to gas
state (water vapor), it gains energy.
- During condensation, when water changes from gas state (water vapor) to liquid
state (liquid water), it loses energy.
- During freezing, when water changes from liqu id state (liquid water) to solid state
(ice), it loses energy.

Gravity force:
• It is the force that causes:
- Water starts to move or change its way of movement when a force affects it.
- There is a main force that affects the water cycle, which is gravity force.

• Water can be pulled downward by gravity force, where it causes :


Energy and Water
Energy and the water cycle:
▌From the previous activities, you have known that when water changes from one state to another, it gains (absorbs) or losses (releases) energy.
▌Gaining or losing energy affects the water particles (molecules) in the air.
▌The movement of air from one place to another in the presence of difference in temperature leads to :
- Changing of liquid water to water vapor and this process is known as "evaporation".
- Changing of water vapor to liquid water (in the form of water droplets) and this process is known as "condensation".

Transfer of energy:
▌Condensation and freezing are two processes occur when water particles lose thermal energy.
▌Melting, evaporation and transpiration (in plant leaves) are processes occur when water particles gain thermal energy.

Evaporation:
▌Through the water cycle, the Sun heats water in oceans, seas, lakes, rivers, streams and other
water bodies.
▌This leads to evaporation of water and changing it into water vapor due to gaining thermal energy.

Transpiration
It is a type of evaporation that takes place through the stomata on the plant's leaves.

Condensation:
Condensation occurs when:
• The air that is saturated with water vapor cools due to decreasing air temperature, so the water vapor changes into liquid water.
• Clouds are formed, where they consist of tiny water droplets that are condensed in the air, so water vapor releases its energy and changes into liquid water.

How are clouds formed?
• Clouds are formed due to condensation of water vapor into water droplets that attach to particles of dust, smoke, .... etc. in the air.
• When very large numbers of these water droplets join together, they form clouds.


بالتوفيق
مستر احمد الباشا